I confess I will probably put a Dinan strut brace in the Woadster, eventually-but it's like the Dinan wheels: yes, they are VERY light, and if I ever drove in the rare atmosphere in which their mass became important, they would serve me well.

But the truth is that I think they look way bitchin'. In my view of things, that's reason aplenty.

Satch Carlson

"The first failure of communication is the belief that any is taking place."

They did add one (or two, rather). See the bars going from the strut towers to the center of the engine bay (towards windshield)? Those are strut braces.

Those weren't "added". They were stock from the factory.

As to any performance oriented car has one...the pictures I posted were of a PROFESSIONAL RACE TEAM racing in one of the highest levels of professional road course racing in the United States, with a lot more budget than you or me, and a strut brace is explicitly allowed in the rules. Yet they choose to not add a $800 brace. For a professional race team, why do you suppose that is so?

Because it adds absolutely no benefit to THIS chassis, that's why. The only benefit to a strut brace on the MZ4 chassis (E86 in particular) is looks, and that can be debatable.

A strut tower brace goes between the two shock towers, like the center one in the previous photo I posted (red one), that one is added and not stock, that is where the flex occurs in convertibles, it will make a difference, if not why does BMW now sell them for the Z4? This from Tischer BMW, "Improve the handling and stability of your Z4 with this OEM BMW Z4 Front Strut Brace! Price includes free ground shipping! (US only)" Even Hamann gets in on it with this, "To make the body even stiffer, HAMANN also offers a two-part strut-tower breach (with HAMANN logo), which is fitted at the front." Rouge Engineering says this about strut tower braces (and they sell them for the Z4), "Who can benefit from a strut bar?
For those that may believe a strut bar is only for "track cars" or "racecars", it is also street driven vehicles that benefit from a properly engineered strut tower bar. Whereas anyone can appreciate the ability for a front suspension to remain constant at all times, other benefits include support of the factory strut towers from "mushrooming". These generally occurs if the vehicle hits large potholes, causing the suspension to compress completely, and then damaging the rim. However, its not only the rim that takes the hit, but the shock tower as well. Over time, if left unprotected, it can cause expensive sheet metal damage."

And lastly read this article from European Car where they state after testing with and without a brace on a MZ4, "Is there a difference? After some spirited runs through the mountains, it's clear the front end is noticeably tighter and better connected to the road, the uncertain turn-in is reduced significantly." You can read the entire write up here: http://www.europeancarweb.com/tuned/epcp_0709_project_z4m/index.html

Again, I ask...Why would a professional raceteam, where budget and rule is not an issue, not run a strut brace when the rules specifically ALLOW it, especially if it improves performace as you claim? In a sports where money is spent like it grows on trees to improve EVERY ASPECT of the car?

And just because BMW sells it it must mean it'll add performance, right? I mean, BMW also tout run-flats as the end-all solution to tires. They'll also sell you a shorter knob and call it a "short shift kit." It's called marketing, BMW/Hamann/Dinan/whoever will make and sell you a strut brace because they know they'll make money from it, and they can sucker you into buying it. Companies will say anything to get you to buy their products. Ever stay up late and watch sports coverage? Notice all the "male enhancement products" they sell? If you can make your "unit" bigger by buying and taking some pills, why wouldn't they be advertising in prime-time, and why wouldn't every male in the United States be hung like Petey North?

I mean, after all, "satisfaction is guaranteed" with male enhancement pills.

RE: EuropeanCar web article...Heck those "journalists" at EuropeanCar must have much more sensitive @ss than I do, since I added a strut brace to my E46 and drove the piss out of it on the track, and frankly...Even on a "soft" chassis like the E46, the strut brace made absolutely NO DIFFERENCE. I have to be honest, I "write" freelance for the car industry. One thing a car journalist has, is integrity (present Roundel staffer/company excepted, of course). The integrity to never bad-mouth a manufacturer and sponsor and say anything even neutral about their product. That's why you read Road and Track rave about the Asstek, or a Suzuki SX4 making the "fun to drive" list on MotorTrend. If a sponsor gave you a strut brace, you're obligated to say in your article that the strut brace is the best thing since sliced bread. Heck it's even better than sliced bread. Take everything you read in any car publication with a grain of salt. Imagine if I were to write what I wrote here in a review of a strut brace...How long I'd keep my "freelance" job.

p.s.: How exactly does adding a top bar between two verticle weight bearing struts "prevent flex" in the convertible? I might be inclined to think that the OE strut brace placement, where it's triangulated and affixed to the firewall/chassis/cowl, would be the way to minimize flex in an already very stiff convertible chassis (did you know the Z4 roadster is the stiffest convertible BMW ever made? It's as stiff as the E46 COUPE, which was already a very stiff chassis), not a bar across the top of the struts.

I provided links that backup my statements, you provide your opinion with no evidence, other than to say, "Why would a professional raceteam...", well I provided a photo of a "professional raceteam" using a strut bar, and as a former Race Chairman, I have seen my share of professional, Club racers, weekend racers and others who do use a strut tower brace.

I have never heard of a "short shift kit" by BMW, so I have no idea on that one.

And of course you want to discredit Eurpoean Car, because apparently you are a part time "journalist", so I would assume your opinion is as worthless as theirs!

Lastly if you are serious about your question about how a strut tower brace can prevent flex than you need to sit down with and engineer and attempt to understand physics. I do not have the time to explain it to you.

Maybe this will help: "A strut bar, strut brace, or strut tower brace (STB) is a mostly aftermarket car suspension accessory usually used in conjunction with MacPherson struts on monocoque or unibody chassis to provide extra strength between the strut towers.

With a MacPherson strut suspension system where the spring and shock absorber are combined in the one suspension unit, the entire vertical suspension load is transmitted to the top of the vehicle's strut tower, unlike a double wishbone suspension where the spring and shock absorber may share the load separately. In general terms, a strut tower in a monocoque chassis is a reinforced portion of the inner wheel well and is not necessarily directly connected to the main chassis rails. For this reason there is inherent flex within the strut towers relative to the chassis rails.

A strut bar is designed to reduce this strut tower flex by tying two parallel strut towers together. This transmits the load of each strut tower during cornering via tension and compression of the strut bar which shares the load between both towers and reduces chassis flex.

On the Saab Sonett mk2 and mk3 the overflow container for the cooling system doubles as a strut bar. The longnose version of the Saab 96 also came with a factory mounted strut bar.

Performance: Resulting from the improved chassis rigidity (similar to that gained from a lower tie bar); may be improved steering precision under high load conditions (cornering and braking). Reduced understeer, tire wear and metal fatigue in the strut tower area may also be experienced.

They finished 3rd on their 2nd race ever in Grand Am Koni Challenge. Which race team did that photo you posted come from and what class did they run in?

And I'm not disputing strut braces may be beneficial to performance. I'm merely disputing strut braces being beneficial to THIS chassis. On an E36 sans cross brace? Sure it helps. On an E30? Heck yes. On a Z3? Definitely. On the Z4? It's worthless and nothing but bling.

I thought the purpose of these forums are to promote open discussion? Maybe I'm wrong. If you can actually explain to me, how on the Z4 chassis, one of the stiffest chassis BMW has ever built in a convertible, and the most stiff chassis BMW has ever built in a coupe, that a cross strut brace would benefit when two braces trangulated to the chassis bulk-head is already present, PLUS a cross brace bolted to the FRAME is already present underneath the car, I'd love to hear it. If an engineer can actually show data that said brace, ON THE Z4, would provide appreciable structural rigidity, I believe everyone participating on these forum would benefit from the discussion.

As for my opinion being worthless, did I say journalist opinions are worthless? They just need to be read with a grain of salt. I've hung around these same journalist and sometimes do the same thing they do, and frankly, if they write for any sizable magazine, they have a very strict "guideline" they need to adhere to, namely, do not bite the hands that feed you. If you have nothing positive to say, say what you need to say in a positive way. Again, if I write what I wrote here for my publication, you can be sure that whatever company supplied me the strut brace will be writing a very scathing letter to my editor even before the publication goes to print. Thank "god" for the relative anonymity of the internet (although I'm sure if Satch were to run a querie into my username he'd find out EXACTLY who I am). Some magazines seems to be above kow-towing to the powers that be, European Car is not one of them.

Playing the victim? Because I never said that. Reference your opinion you are the one who mentioned "integrity", and than said Journalists have the "integrity to never bad-mouth a manufacturer and sponsor and say anything even neutral about their product." And in the same paragraph you admit your a journalist. Your compairison, not mine! And what does this mean, "although I'm sure if Satch were to run a querie into my username he'd find out EXACTLY who I am", you sound full of yourself. If you are of the opinion that the brace is usless I am ok with that, your opinion.

I stated my opinion, backed it up with links, and facts and now I am done with this conversation. Enjoy!

Lastly if you are serious about your question about how a strut tower brace can prevent flex than you need to sit down with and engineer and attempt to understand physics. I do not have the time to explain it to you.

Maybe this will help: "A strut bar, strut brace, or strut tower brace (STB) is a mostly aftermarket car suspension accessory usually used in conjunction with MacPherson struts on monocoque or unibody chassis to provide extra strength between the strut towers.

A strut bar is designed to reduce this strut tower flex by tying two parallel strut towers together. This transmits the load of each strut tower during cornering via tension and compression of the strut bar which shares the load between both towers and reduces chassis flex.

Maybe you need to think about physics yourself. Tying the front (or rear) strut towers together with a brace does nothing but aggravate the inherent flex of a roadster's chassis because it flexes most across the center of the floorpan. This may be obviated in a car with a roll cage that braces across the doors and from side to side, but on a street vehicle, I can see no way that making the front stiffer is not going to increase chassis flex in the middle.

Let's add one more cheap shot to this discussion:
No guy who ever spent a lot on a strut brace will ever admit he wasted his money.

Maybe you need to think about physics yourself. Tying the front (or rear) strut towers together with a brace does nothing but aggravate the inherent flex of a roadster's chassis because it flexes most across the center of the floorpan. This may be obviated in a car with a roll cage that braces across the doors and from side to side, but on a street vehicle, I can see no way that making the front stiffer is not going to increase chassis flex in the middle.

Let's add one more cheap shot to this discussion:
No guy who ever spent a lot on a strut brace will ever admit he wasted his money.

Except that you apparently forgot that the roadster has a cross brace that adds support to the car! I spent nothing for my cross brace, it came on the car when I purchased it. My father in law an engineer could explain it to you but alais your mind is made up!